Chronic obstructive pulmonary disease (COPD) is the most common chronic disease of the airways that is caused in 90 % of cases by smoking. COPD is a preventable and treatable disease. However, many patients do not know that they suffer from the disease, so the number of unreported cases of patients is very high. In this article, you will find important information on the epidemiology, etiology, pathophysiology and diagnosis, as well as the differential diagnosis and treatment of COPD.

00:00
The other aspect of
lung function tests thatyou need to think about, are the flow volume
loops and the lung volumes. So, the lung volumesare increased in COPD, the patient has bigger
overall lung volumes than normal. That mayseem surprising but that relates to the air
trapping that we discussed that I mentionedearlier, and that I'll discuss in more detail
in a second. The reason for the increase inlung volume is that the residual volume, the
amount of air left in the lung at the endof expiration, increases. So although the
lung volumes are larger, it's useless volume,it's not air that shifting during inspiration
and expiration. It's just the residual volumethat's driving the increase in lung volume.
If the patient has emphysema, then they'velost a lot of surface area for gas exchange
because of the alveolar destruction. And thatmeans the transfer factor which measures the
ability of oxygen to get in from the lungsinto the blood, goes down. So a low transfer
factor suggest emphysema.
01:11
In addition, the alveolar structures are required
for splinting open the airways, as you breath out.
01:18
So on expiration, there tends to be,
there's a positive pressure in the thoracic cavity,and that squeezes air out of the lungs, but
it also squeezes the bronchi, taking the airout of the lungs. And if the bronchi have
lost their structural support, then there'llbe a tendency for them to be closed off by
that pressure, the expiratory pressure.
01:39
And that's called dynamic airways collapse and
occurs in emphysema where the loss and destructionof the alveoli means the bronchi are not splintered
open and cannot combat the positive pressureof expiration. And you can see that on a flow
volume loop, which is illustrated here onthe right hand side of the slide. You can see
that the person with emphysema, the solidblue line, what happens is that as they breathe
out there’s a rapid increase in flow initially,and then there is a sudden decrease in flow
due to this dynamic airways collapse, andthat’s followed by a prolonged phase of low
flow expiration. The other investigationsyou need to do with somebody with COPD, will
clear your chest X rays is useful, but actuallyit’s not that abnormal in most patients.
In patients with significant disease, it willshow a degree of hyper-inflation with reduced
lung markings, more visible anterior rib endsthan normal, perhaps flattened diaphragms and
a small heart. You can see bullae on a chestX ray so some people who have quite expanded
lung cysts due to COPD, that is bullus thatis visible on a chest X ray. And also a chest
X ray is important to identify complications,pneumonia, pneumothorax, and chronically,
to make sure that they don’t have cancer.
02:52
The CT scan is used to identify patients who
have emphysema, to look for bullae, and perhapsto look for co-existent bronchiectasis or other
complications. So, these are some examplesof X rays you might see. The X ray on the
left hand side of the slide is somebody witha hyperexpanded lungs due to COPD and basically
you see black lungs, very long thin lungs,and the heart is stretched as well, and that’s
a hyperexpanded pair of lungs with oligaemiclung fields. The middle CT scan shows centrilobular
emphysema, and what you can see a black holeis where there’s been lung destruction with
the grey material around the outside beingthe normal lung. That’s a sort of Swiss cheese
lung, it’s got holes in it. The last scanis somebody who also has some emphysema but
that’s distributed in a different way, it’sdifferent in being centrilobular in the middle
of the lung lobules. It’s actually aroundthe septum, around the edges of the lung lobules,
and the number one arrow is pointed to a verylarge area of air within a single cyst and that is
a bullus and that can happen in some patientswith COPD. What other investigations are useful
in COPD? Well, actually not much. Lung function,chest X ray, some patients need a CT scan, blood tests,
you may want to measure the alpha-1-antitrypsinlevels to see whether they have early onset
emphysema, if they are relatively young patients,especially if they have basal emphysema on
their CT scan. Normal blood tests for bloodcount, Fbc, U+E, LFT are all normal. Some
patients, you need to do an echocardiogramand ECG and there’s two reasons for that- one,
the main differential diagnosis for somebodywith COPD would be cardiac breathlessness,
congestive cardiac failure, or a valvularproblem such as aortic cyanosis, and you may need
to exclude that as a cause of their breathlessness.
04:46
And the other reason why you need to do an echocardiogram
and ECGs is those patients with chronic hypoxiamay develop cor pulmonale and you need an echocardiogram
to measure the pulmonary hypertensionthat could be present in those circumstances.
Invasive tests such as bronchoscopy or lungbiopsy are not needed for patients with COPD,
they are not needed for diagnosis at all.
05:06
So, how do you recognize patients with COPD.
It’s a combination of gradually worseningbreathlessness on exertion over years or months
with a significant pack year history, 25 to30 pack year history, therefore, most patients
will be aged over 50 or so. Plus obstructive spirometry.
05:25
The chest X ray often looks normal,
the main differential diagnosis is congestivecardiac failure, chronic PEs, that will be a
shorter history, and they’ll have an abnormaltransfer factor, and importantly the lung
volumes and spirometry will be normal. Chronicasthma, there’s no history of smoking, there’s
definitely a past history of asthma in mostof those patients. And pulmonary fibrosis.
And this is where crackles are important,because if you hear crackles, that’s not due
to COPD, and in addition the lung functionpattern you get with pulmonary fibrosis is different,
it’s a restrictive lung function with anincreased FEV1 to FVC ratio and usually
a fall in transfer factor as well.

About the Lecture

The lecture Chronic Obstructive Pulmonary Disease (COPD): Tests and Investigations by Jeremy Brown, PhD is from the course Airway Diseases.

Included Quiz Questions

Which of the following is NOT a feature of lung function in an emphysematous patient?

Decreased residual volume

Increased total lung volume

Low transfer factor

On expiration, there is dynamic airway collapse

There is a dip in the expiratory curve on the flow volume loop

Which of the following is responsible for the defense mechanism of pursed lip breathing in a patient with severe emphysema?

To prevent dynamic airway obstruction in emphysema

To increased total lung volume in emphysema

To decrease the residual volume in emphysema

To increase the peak expiratory flow in emphysema

To prevent cyanosis in emphysema

Which of the following is NOT a finding on the X-ray of a patient with severe emphysema?

Boot shaped heart

Increased intercoastal distance

Prominent bullae

Reduced lung markings

Flattened diaphragms

Which of the following complications is responsible for the pneumothorax in a patient with COPD?

Subpleural bullae

Hyperinflated lungs

Expanded intercostal spaces

None of the options

Infections

Which of the following is NOT a common complication of emphysema?

Cavitation

Pneumothorax

Bronchiectasis

Pneumonia

Respiratory failure

What is the purpose of performing an echo-cardiogram periodically in a patient with COPD?

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